Hand-operated impact torque wrench



Jan. 8, 957 F. w. LIVERMONT 2,776,588

HAND-OPERATED IMPACT TORQUE WRENCH Filed Dec. 50, 1954 3 Sheets-Sheet l 6 & g I z Q M II Q Q K2 Q w M g 3 s Q N 3 o 4 *0 L Q INVENTOR'. k FZA/VA WZ/I/EPMO/VT Jan. 8, 1957 F. w. LIVERMONT 2,776,583

HAND-OPERATED IMPACT TORQUE WRENCH 5 Sheets-Sheet 2 Flled Dec. 50, 19.54

MW QM 1957 F. w. LIVERMONT 2,776,588

HAND-OPERATED IMPACT TORQUE WRENCH Filed Dec. 30, 1954 5 Sheets-Sheet 3 Ill 4 45 INVENTOR.

ia/m Wz/we/vm r Byi fi x United States Patent HAND-OPERATED IMPACT TORQUE WRENCH Frank W. Livermont, Duarte, Calif. Application December 30, 1954, Serial No. 478,569 16 Claims. (11. 81--52.3)

My invention relates to hand-operated impact torque Wrenches, and included in the objects of my invention are:

First, to provide a wrench of this type which includes a ratchet drive for advancing a bolt or nut until snug, whereupon the operator, on forcing the wrench handle while the ratchet drive is held by the snug bolt or nut from further movement, causes a hammer blow to be imparted, or several such impacts if desired.

Second, to provide a wrench of this type wherein conversion from a ratchet operation to an impact operation occurs automatically without special action on the part of the operator. 1

Third, to provide a wrench of this type which is readily adjusted to impart the desired impact and may be de-. pended upon to repeatedly deliver the desired impact.

Fourth, to provide a wrench of this type which is equally applicable for loosening as well as tightening a bolt or nut or similar device, all with a minimum of adjustment.

Fifth, to provide a Wrench of this type which is inherently rugged of construction and dependable in operation.

With the above and other objects in view, as may appear hereinafter, reference is directed to the accompanying drawings in which:

Figure 1 is a fragmentary, longitudinal sectional view of my impact torque wrench, shown in its normal or inactive position;

Fig. 2 is a reduced perspective view of the impact torque wrench;

Fig. 3 is a perspective view of the pawl member;

Fig. 4 is a longitudinal sectional view similar to Fig. 1, showing the impact torque wrench immediately prior to release of the hammer;

Fig. 5 is a similar sectional view, showing the position of the parts of the impact torque wrench immediately following operation of the hammer; v

Fig. 6 is a fragmentary, longitudinal sectional view, showing the operation of the impact torque wrench when employed as a ratchet wrench;

Fig. 7 is a transverse sectional view through 77 of Fig. 1;

Fig. 8 is a transverse sectional view through 88 of Fig. 1, showing the kep balls in their radially extended position;

Fig. 9 is a transverse sectional view, taken through 9-9 of Fig. 5 showing the key balls in their radially re tracted position; I

Fig. 10 is a fragmentary, longitudinal sectional view of a modified form of my impact torque wrench in its ratcheting position; and

Fig. 11 is a similar fragmentary, longitudinal sectional view, showing the modified wrench in its torque-applying position immediately prior to delivery of an impact, this view corresponding to Fig. 4.

My impact torque wrench comprises a tubular handle 1 terminating at one end in an integral ratchet housing 2. The ratchet housing defines a cylindrical cavity closed at one axial end and provided with a cover 2a at its other end. The housing is disposed eccentrically with respect to the handle 1 and with its axis at right angles thereto.

Within the ratchet housing 2 is a ratchet wheel 3, preferably mounted relative to the housing on ball bearings 4. The periphery of the ratchet wheel 3 is provided with ratchet teeth 5, preferably divided axially by a central annular groove 6. The ratchet wheel 3 is provided with a polygonal axial bore (shown as square in the drawings) which receives a drive mandrel 7 of corresponding cross-section.

The drive mandrel 7 is axially slidable so as to protrude from either end and is provided with suitable ball detents 8 to hold in either of its extended positions, shown by solid line and broken line in Fig. 7. The projecting end of the drive mandrel is intended to receive a conventional wrench socket (not shown).

Disposed within the handle 1 at its end adjacent the housing 2 is a pawl structure 9 having a socket in one end and terminating in a pawl 10 at its other end. The tip of the pawl is centered relative to the longitudinal axis of the pawl structure and one side of the pawl structure is relieved, as indicated by 11, behind the pawl 10.

The relieved portion 11 of the pawl structure 9 is divided by a longitudinal rib 12 of arcuate profile which is adapted to ride in the central groove 6 of the ratchet wheel 3 and maintain the pawl structure in alignment therewith. A stop pin 13 protrudes radially from the pawl structure and rides in a slot 14 provided in the wall of the handle 1.

The socket end of the pawl structure 9 receives the reduced end of a hammer 15, the extremity of which is adapted to strike against the bottom of the socket in the pawl structure to transfer an impact from the hammer to the pawl 10 and to the ratchet wheel 3.

a The handle 1 is normally retained with its striking end spaced from the bottom of the socket in the pawl structure by means of a pair of key balls 16 disposed in a diametrically extending cross bore formed in the hammer. The hammer is provided with a central longitudinally extending socket which receives a trip shaft 17 having anannular groove 18. The extremity of the pawl structure is provided with a counterbore 19.

The key balls 16 are adapted to occupy a radially outer position, as shown in Figs. 1 and 8, wherein they project into the counterbore 19 of the pawl structure and thus prevent movement of the hammer into the socket in the pawl structure. They are held in such position by the trip shaft 17. The trip shaft is movable, as shown in Figs. 4, 5, and 9 to align the annular groove 18 with the key balls so that they may move radially inward and release the hammer 15.

Movement of the hammer 15 is limited by a pin 20 which projects radially into a slot formed in the side wall of the pawl structure 9. Similarly, a pin 21 projects radially inward to ride in a slot formed in the trip shaft 17 so that movement of the trip shaft is limited.

A spring 22 surrounds the hammer 15 and bears against the socket extremity of the pawl structure 9. A ring 23 is interposed between the spring 22 and the pawl structure to cover the counterbore 19. A spring 24 is interposed between the inner end of the trip shaft 17 and the .socket within the hammer 15 so as to urge the trip shaft towards an outer position relative to the hammer. The springs 22 and 24 are relatively light springs, merely to provide a biasing force under normal conditions wherein the key balls are maintained in their radially outer position, shown in Figs. 1 and 8.

The extended portion of the handle 1 is slightly enlarged to form a power spring chamber 25 closed at its extremity by an adjustment screw 26. The hammer 15 extends into the spring chamber 25 and is enlarged to form a head 27. I

Positioned within the spring chamber 25 is a power spring 28 which bears against the head 27 of the hammer 15 and the adjustment screw 26. The adjustment screw 26 is provided with a screw-threaded bore which receives a correspondingly screw-threaded adjustable trip stop 29 in the form of a rod reduced at one end to enter the bore of the hammer 15 and engage the trip shaft 17.

As will be brought out hereinafter, the hammer 15 and pawl structure 9 are intended to pivot slightly within the hammer 1 as well as reciprocate, the pivotal action being employed when the wrench is used merely as a ratchet wrench and need be only sufiicient to permit the pawl to pass over the ratchet teeth 5. To accomplish this pivotal action, a fulcrum screw 30 projects inwardly and rearwardly through the handle 1 at the inner end of the power spring chamber 25, so as to bear against one margin of the hammer head 27 as shown best in Figs. 1 and 6. The power spring in its engagement with the hammer head urges the hammer and pawl structure pivotally so that the pawl 10 is yieldably held in engagement with the ratchet teeth 5.

Operation of my impact torque wrench shown in Figs. 1 through 9 is as follows:

When the wrench is used as a ratchet wrench, the pawl 10 occupies the position shown in Fig. 6 and the head 27 of the hammer 15 bears against the fulcrum screw 30 under urge of the power spring 28. Under urge of the power spring the entire assembly involving the pawl structure 9 and hammer 15 tend to pivot about the fulcrum defined by the fulcrum pin 30 so as to urge the pawl tip 10 against the ratchet wheel 3. In this position the ratchet wheel may be rotated by moving the pawl 10 clockwise, as viewed in Fig. 6, and the pawl may be advanced counterclockwise to a new position so as to etf ect rotation of the drive mandrel 7.

When the drive mandrel 7 is restrained from rotation and the handle 1 is rotated clockwise, as viewed in the drawings, the pawl tip 10 fails to advance the ratchet wheel 3, instead the entire assembly, including the pawl structure 9 and hammer 15, moves to the right, compressing the power spring 28. Compression of the spring 28 continues until the trip shaft 17 is restrained by the trip stop 29 and the key balls 16 move opposite the groove 18 in the trip shaft. This condition is shown in Fig. 4. Immediately thereafter the key balls move radially inward, releasing the hammer, so that the hammer is caused by the action of the power spring 28 to strike the bottom of the socket in the pawl structure 9. This action causes the pawl tip 10 to deliver an impact blow against the teeth of the ratchet, as indicated in Fig. 5 of the drawings.

Upon reversing the direction of movement of the handle 1, that is, by rotating the handle counterclockwise, the head 27 of the hammer 15 is restrained, and the pawl structure 9 is caused to move forward by means of the spring 22 until the counterbore 19 registers with the key balls 16. The trip shaft 17 is then free to move rearwardly, or to the right as viewed in the drawings, under urge of the spring 24, forcing the key balls radially outward into the initial position shown in Fig. 1. Thus by oscillating the handle 1 a series of blows may be imparted to the ratchet wheel 3.

If the socket element is on the lower side of the mandrel 7, as viewed in Figs. 1 and 2, the action of the wrench tends to tighten the bolt or nut driven by the socket member. If the socket member is mounted on the upper end of the mandrel 7, as viewed in Figs. '1 and 2, the action of the wrench will tend to loosen the bolt or nut.

Reference is now directed to the construction shown in Figs. and 11. The structure here shown includes a handle 31 corresponding to the handle 1. The extended portion of the handle is provided with a power spring chamber and spring corresponding to the chamber 25 and power spring 28.

The operating end of the handle 31 is provided with a housing 32 substantially centered relative to the axis of the handle. The housing 32 journals a ratchet 33. In place of the pawl structure 9 there is provided a pawl carrier 34 which extends into the housing 32 and terminates in a clevis 35 having a clevis pin 36 which oscillatably supports a double-acting pawl 37.

The pawl 37 is provided with oppositely extending arms 38, terminating in pawl tips 39, either one of which is adapted to engage the ratchet 33 so that the ratchet may be driven in either direction by oscillation of the handle 31.

The double-acting pawl 37 is urged to either extreme position by means of an over-center lug 40 extending toward the handle 31 and engaged by a detent 41 mounted in the pawl carrier 34 and urged outwardly by a spring 42. A spring 43 urges the pawl carrier 34 into the housing 32. A pin 44 extends laterally from the pawl carrier 34 and rides in a slot 45 provided in the handle The outer end of the pawl carrier 34 extending within the handle 31 is identical in construction to the corresponding end of the pawl structure 9 shown in the first described structure; that is, the pawl carrier is provided with a socket which receives the hammer 15 and the key ball assembly. The extended portion of the handle 31 (not shown) in Figs. 10 and 11 is substantially identical to that shown in the first described structure.

Operation of the construction shown in Figs. 10 and 11 is as follows:

When the wrench is used as a ratchet wrench, the pawl occupies either the solid or broken line position shown in Fig. 10. The pawl is moved to either position by conventional manually operated means, not shown. Under such conditions the hammer 15 rests against the shoulder formed at the inner end of the chamber 25. In this case the fulcrum screw 30 is omitted.

When the ratchet encounters resistance, the pawl 37 pivots from the solid line position shown in Fig. 10 toward the solid line position shown in Fig. 11, causing the pawl carrier 34 and hammer 15 to move to the right, as viewed in these figures, compressing the power spring 28 as in the first described structure.

After a predetermined movement of the pawl carrier 34 and hammer 15, the hammer is released in the same manner as in the first described structure, imparting a blow to the pawl carrier which is transmitted through the pawl 37 to the ratchet wheel 3. The direction in which the blow is imparted depends upon which pawl tip 39 is in contact with the ratchet wheel.

Having fully described my invention, it is to be understood that I do not wish to be limited to the details herein set forth, but my invention is of the full scope of the appended claims.

I claim:

1. An impact torque wrench, comprising: a ratchet member adapted for a driving connection with a fastening device; an arm rotatable about said ratchet member; a pawl carried by said arm for driving said ratchet member as said arm is oscillated; a hammer also carried by said arm, said hammer being movable to deliver an impact to said pawl thereby to deliver an impact to said ratchet member; and means operative, upon resistance of said ratchet member to turning, by said pawl to release said hammer.

2. An impact torque wrench, comprising: a ratchet member adapted for driving connection with a fastening device; a tubular arm rotatable about said ratchet member; a pawl mounted in said arm .for engaging and turning said ratchet member; means movable axially .in said arm by said pawl on resistance of said ratchet member to movement by said pawl; a hammer movable by said means; and interlocking elements between said axially movable means and said hammer to release said hammer to impart an impact through said means to said pawl and ratchet member.

3. An impact wrench as set forth in claim 2, wherein: said pawl is rigidly connected to said axially movable means.

4. An impact wrench as set forth in claim 2, wherein: said pawl is a double-acting pawl having two arms alternatively engageable with said ratchet member to drive said member in either direction, and is pivotably connected to said axially movable means.

5. An impact torque wrench, comprising: a tubular handle; a ratchet housing at one end thereof; a ratchet member journaled in said housing and arranged to apply a driving force to a fastening device; a reciprocable pawl support in said handle; a pawl connected with said pawl support for turning engagement with said ratchet member; a hammer within said handle for striking said pawl support to impart an impact through said pawl to said ratchet member; a power spring for driving said hammer; an interlocking means between said pawl support and said hammer adapted, when said pawl encounters resistance in turning said ratchet member, to cause said hammer to compress said power spring; and means operable upon predetermined movement of said hammer and pawl support to release said interlocking means to actuate said hammer.

6. An impact torque wrench as set forth in claim 5, wherein: said pawl is an integral part of said pawl support.

7. An impact torque wrench as set forth in claim 5, wherein: a fulcrum element is provided to cause limited pivotal movement of said hammer and pawl support; said pawl is an integral part of said pawl support and movable on pivotal movement of said pawl support and hammer to and from said ratchet member in a radial direction; and said power spring is arranged when said hammer engages said fulcrum element to exert a bias ing force, urging said pawl in a radial direction toward said ratchet member.

8. An impact torque Wrench as set forth in claim 5, wherein: said pawl is a double-acting pawl having two arms alternatively engageable with said ratchet member to drive said member in either direction and is pivotally connected to said pawl support.

9. An impact torque wrench, comprising: a tubular handle; a ratchet housing at one end thereof; a ratchet member journaled in said housing and arranged to apply a driving force to a fastening device; a reciprocable pawl support in said handle; a pawl connected with said pawl support for turning engagement with said ratchet member; a reciprocable hammer telescoping into said pawl support; a power spring for driving said hammer; key elements in said hammer adapted to occupy a radially outer position interlocking said hammer with said pawl support and a radially inner position freeing said hammer for an impact blow against said pawl support for transmittal to said pawl and ratchet member; a trip member slidable in said hammer between a position holding said key elements in their radially outer position and freeing said key elements for radially inward movement; means fixed in said handle for causing said trip member to release said key elements upon predetermined movement of said hammer and pawl support against said spring, thereby to actuate said hammer.

10. An impact torque wrench as set forth in claim 9, wherein: said pawl is an integral part of said pawl support.

11. An impact torque wrench as set forth in claim 9, wherein: a fulcrum element is provided to cause limited pivotal movement of said hammer and pawl support; said pawl is an integral part of said pawl support and movable on pivotal movement of said pawl support and hammer to and from said ratchet member in a radial direction; and said power spring is arranged when said hammer engages said fulcrum element to exert a biasing force, urging said pawl in a radial direction toward said ratchet member. Y

12. An impact torque wrench as set forth in claim'9, wherein: said pawl is a double-acting pawl having two arms alternatively engageable with said ratchet member to drive said member in either direction and is pivotally' connected to said pawl support.

13. An impact torque wrench, comprising: a tubular handle; a ratchet housing at one end thereof; a ratchet member journaled in said housing and arranged to apply a driving force to a fastening device; a coaxial pawl support and hammer slidably mounted in said handle; means urging said pawl support and hammer to a relatively extended position; key means locking said pawl support and hammer in their relatively extended position for movement as a unit in said handle; a pawl connected with said pawl support for turning engagement with said ratchet member and adapted to effect axial movement of said pawl support and hammer in said handle upon restraint of said ratchet member; a power spring adapted to be compressed by said hammer on axial movement of said pawl support and hammer; and trip means for said key means to release said hammer for an impact blow against said pawl support thereby to transmit said impact to said pawl and ratchet member.

14. An impact torque wrench as set forth in claim 13, wherein: said pawl is an integral part of said pawl support.

15. An impact torque wrench as set forth in claim 13, wherein: a fulcrum element is provided to cause limited pivotal movement of said hammer and pawl support; said pawl is an integral part of said pawl support and movable on pivotal movement of said pawl support and hammer to and from said ratchet member in a radial direction; and said power spring is arranged when said hammer engages said fulcrum element to exert a biasing force, urging said pawl in a radial direction toward said ratchet member.

16. An impact torque wrench as set forth in claim 13, wherein: said pawl is a double-acting pawl having two arms alternatively engageable with said ratchet member to drive said member in either direction and is pivotally connected to said pawl support.

References Cited in the file of this patent UNITED STATES PATENTS 2,264,012 Wasson Nov. 25, 1941 2,566,661 Hamlin Sept. 4, 1951 2,573,469 Maclay Oct. 30, 1951 2,683,511 McHugh July 13, 1954 2,691,910 Griak et a1. Oct. 19, 1954 2,707,892 Holmes May 10, 1955 2,712,254 Schodcberg July 5, 1955 FOREIGN PATENTS 965,788 France Feb. 22, 1950 

